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Florida Reef Resilience Program

Disturbance Response Monitoring

Quick Look Report:

Summer 2019

This report was prepared by the author under contract for The Nature Conservancy under the cooperative

agreement award #NA16NOS4820106 from the National Oceanic and Atmospheric Administration's

(NOAA) Coral Reef Conservation Program, U.S. Department of Commerce. The statements, findings,

conclusions, and recommendations are those of the author(s) and do not necessarily reflect the views of

NOAA, the NOAA Coral Reef Conservation Program, or the U.S. Department of Commerce.

INTRODUCTION

The Florida Reef Resilience Program (FRRP) is a collaborative effort among local, state, and

federal environmental managers, scientists, conservation organizations, and reef users to develop

resilience-based management strategies for anticipating and addressing climate change and other

stressors on Florida’s coral reefs. Precipitated by the severe coral bleaching event in the Florida

Keys in 2005, the FRRP developed the Disturbance Response Monitoring (DRM) program to

assess reef condition annually during the months of peak thermal stress. Since 2005, the partners

of the DRM program have conducted annual surveys to document the extent and severity of

coral bleaching and disease on the Florida Reef Tract (FRT).

The primary goals of the DRM program have always been to provide a condition report and the

annual status of bleaching along the FRT. This information is used to identify resilient areas of

the reef, promote appropriate management or conservation strategies of more resilient and less

reef areas, and aid management in research and restoration decisions. In addition to the extensive

dataset the DRM program provides, it offers the opportunity for partners from across the

jurisdictions of the FRT to work together under a unified effort. Collaborating across agencies,

universities, and organizations allows for multiple sources of input and expertise and generates

transparency across managers and researchers. This is becoming more important as the threats to

the FRT continually grow.

During its tenure, the DRM program has modified its experimental design to account for new

disturbances and has adapted its protocols in response to the outbreak of Stony Coral Tissue Loss

Disease (SCTLD). SCTLD is a lethal coral disease that, since 2014, has spread through nearly

the entire FRT with the exception of the Dry Tortugas (at the time of writing this report in early

2020). The cause of the disease remains unknown, but it is affecting over half of the coral

species found on the FRT. The large network of partners in the DRM program offers a unique

opportunity to assess SCTLD on a broad scale across the FRT. The assessments can be

completed in a three-month period, which offers a rapid and time sensitive evaluation of FRT

condition and SCTLD distribution and prevalence.

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The DRM program uses multiple resources to help predict the onset of coral bleaching and the

presence of coral disease, including SCTLD, prior to the start of the survey season. In July of

2019, the NOAA Coral Reef Watch Bleaching Alert System reported a bleaching ‘Watch’ for

Southeast Florida mainland reefs and a ‘Warning’ for Florida Keys reefs, due to rapidly

increasing sea surface temperatures. While temperatures in Southeast Florida had increased

enough to put the area under a bleaching ‘Warning’ by mid-August, those temperatures leveled

out and decreased by the end of September. In contrast, temperatures in the Florida Keys

experienced a sharp increase through the month of August, putting the region under a bleaching

‘Alert Level 1’ and eventually ‘Alert Level II’ by the end of the month.

Prior to the start of the 2019 DRM survey season, SCTLD had been reported spreading west in

the Lower Keys (FWC & FKNMS divers, pers. comm.), but there were no reports of it in the

Marquesas. However, this may have been due to underreporting because of the difficulty in

accessing that region, and only a few reconnaissance surveys had been completed there. To

determine the potential spread of SCTLD into the Marquesas, the DRM program organized a

research cruise targeting areas of known hardbottom and reef habitat. The 2019 DRM season

marked the first year that the Marquesas subregion had been included in the effort since 2007,

when only six sites were surveyed.

During the 2019 DRM season (between August and October), 82 surveys were completed in

southeast Florida, 124 in the Florida Keys, 31 in the Marquesas, and 48 in the Dry Tortugas. No

surveys were completed north of the Palm Beach subregion. As in 2018, surveys were not

conducted in the Martin County subregion due to adverse weather and poor water quality

resulting from releases from Lake Okeechobee. Therefore, the results of this report do not reflect

conditions experienced in the Martin County subregion during the 2019 DRM season.

Survey partners for the 2019 season included Biscayne National Park, Broward County, Dry

Tortugas National Park, Florida Department of Environmental Protection, Florida Fish and

Wildlife Conservation Commission (FWC), John Pennekamp Coral Reef State Park, Keys

Marine Laboratory, Miami-Dade County, Mote Marine Laboratory, National Oceanic and

Atmospheric Administration (NOAA), Nova Southeastern University, Palm Beach Zoo,

Rosenstiel School of Marine and Atmospheric Science, and The Nature Conservancy.

This summary report describes the prevalence of coral bleaching, paling, and disease in 2019 as

assessed through belt transect surveys. Prevalence values were calculated by pooling all corals

by sites and by zones within a subregion. Reef zones were classified by cross-shelf position,

distance from shore, and depth, while subregions were stratified latitudinally. In addition to the

belt transect surveys, if time allowed, a Roving Diver Survey (RDS) was conducted at each site

to better detect the occurrence of SCTLD across the FRT. RDS were implemented to increase the

survey area at a reef. Case definitions and other information on SCTLD are compiled by the

Florida Keys National Marine Sanctuary and can be found at https://floridakeys.noaa.gov/coral-

disease/.

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METHODOLOGY

Belt Transects

The DRM program surveys coral populations using a probabilistic sampling design based on

how corals are distributed spatially within and across different subregions and zones of the FRT.

For the 2019 DRM season, 323 potential survey sites were allocated across 39 discrete reef zones

in 12 subregions.

Sites were randomly selected, and surveys consisted of two replicate 1x10 m belt transects that

were haphazardly placed within a 100x100 m sample area. At all sites, the indicators recorded

for all stony corals >4 cm were size (max diameter and height) and condition, as determined by

the presence of bleaching, paling (i.e., the precursor to bleaching), disease, and percent morality.

Percent mortality was assigned as either old mortality, recent mortality due to disease, or recent

mortality due to other factors (biotic or abiotic). If disease was the cause of recent mortality,

surveyors described the tissue loss pattern and rate of spread, and identified the condition using a

three-letter coral disease identification code. The identification code for SCTLD was added to

the DRM data entry system in 2019 as ‘STL’ (Stony Tissue Loss).

From the surveyed population, prevalence values of bleaching alone, bleaching and paling

combined, and disease were calculated by pooling coral data by site and by zone within each

subregion. Prevalence values represent the percent of corals affected within a site or zone

population. Prevalence values were compared across zones and subregions to identify spatial

differences in the severity of coral bleaching and paling as well as identify spatial patterns of

coral diseases.

Roving Diver Survey

Once two belt transects had been completed at a site, divers completed one or two separate RDS

if time allowed. The diver(s) conducting the RDS swam outside of the belt transect area and

tallied corals >10 cm in diameter in one of three categories: healthy, diseased, or 100% recently

dead from disease. Only corals experiencing active tissue loss from disease or 100% tissue loss

from disease were recorded during the RDS survey. Corals with conditions such as Dark Spot

Syndrome or that had discolored tissue were not recorded as diseased. Due to the wide range of

symptoms exhibited by corals with SCTLD, surveyors were not asked to distinguish between the

different types of diseases during the RDS. Thus, any corals with active tissue loss from disease

were recorded.

The RDS survey was limited to seven target coral species known to be highly susceptible to

SCTLD: Colpophyllia natans, Dichocoenia stokesii, Diploria labyrinthiformis, Meandrina

meandrites, Montastraea cavernosa, Orbicella faveolata, and Pseudodiploria strigosa. While

survey time was recorded for each RDS, the size of the area surveyed, and the duration of the

survey varied across sites.

Similar to the belt transect data, prevalence values of disease from the roving diver surveys was

calculated by pooling coral data by site within each subregion. Disease prevalence values

represent the percent of the surveyed population at a site that were experiencing active tissue loss

from disease.

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2019 DRM RESULTS

Belt Transect Results

A total of 285 sites were completed across 11 subregions for the 2019 DRM season. Six sites

were completed in North Palm Beach, nine in South Palm Beach, two in Deerfield, 65 in

Broward-Miami, 15 in Biscayne, 27 in the Upper Keys, 10 in the Mid-Upper Keys Transition, 18

in the Middle Keys, 54 in the Lower Keys, 31 in the Marquesas, and 48 in the Dry Tortugas.

The prevalence of colonies exhibiting signs of bleaching and paling was pooled by sites (Table 1

and 2) and by zones (Figure 1 and 2) within each subregion. Prevalence values were broken into

three categories: mild (0-20%), moderate (21-50%), and severe (>50%). When looking at

bleached and partially bleached colonies only (i.e., excluding pale colonies), mild bleaching

occurred at 249 of the 285 sites surveyed (Table 1). Moderate bleaching occurred at 33 sites,

including 11 sites in the Broward-Miami subregion and 11 in the Dry Tortugas subregion. Only

three sites were recorded with severe bleaching: one each in North Palm Beach, South Palm

Beach, and Broward-Miami. All three severely bleached sites, however, had less than five coral

colonies recorded along the belt transects. When prevalence data was pooled by zone within the

subregions, all subregion-zones were recorded with mild bleaching prevalence (0-20%; Figure

1).

Table 1. Total number of sites within each subregion recorded with mild, moderate or severe

bleaching prevalence of coral colonies.

Mild 0-20%Moderate

21-50%

Severe

>50%

North Palm Beach 6 45 5 1

South Palm Beach 9 100 6 2 1

Deerfield 2 49 2

Broward-Miami 65 1262 53 11 1

Biscayne 15 784 12 3

Upper Keys 27 1476 27

Mid-Upper Keys Transition 10 552 10

Middle Keys 18 968 18

Lower Keys 54 4510 48 6

Marquesas 31 3666 31

Dry Tortugas National Park 48 4232 37 11

Total 285 17644 249 33 3

SubregionTotal

Sites

Total

Corals

# of Sites with Bleaching Prevalence

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Figure 1. Bleaching prevalence of surveyed coral colonies by subregion-zone.

When paling was included within the bleaching analysis, prevalence values increased to

moderate (21-50%) and severe (>50%) in over half the sites surveyed in 2019 (Table 2). Sites

with moderate bleaching and paling occurred in at least one zone of all surveyed subregions

except for Deerfield. The Marquesas, Dry Tortugas, and Broward-Miami subregions had the

highest number of sites with moderate bleaching and paling. The Dry Tortugas also had 22 sites

with severe bleaching and paling. Pooled by subregion-zone, 16 of the 31 subregion-zones were

recorded with moderate bleaching and paling (Figure 2). While the outer reef of South Palm

Beach had severe paling at 73%, this high percentage was likely the result of the low density of

corals in that area (11 colonies total within the subregion-zone surveys). All reef zones in the

Middle Keys subregion were recorded with less than 20% bleaching and paling (Figure 2).

Paling (a precursor to bleaching where coral color is lighter than normal) is included within the

prevalence analysis because any visible loss of color indicates significant stress on a coral

colony. It is advised, however, that paling results be interpreted with caution, due to the

subjectivity inherent in how divers across the wide range of DRM surveyors interpret variations

in coral color in the field.

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Paling of coral tissue is most commonly attributed to thermal stress but can also be the result of

the initial phases of SCTLD. Discoloration of tissue and paling from disease can often be

difficult to distinguish in the field and can occur simultaneously if the corals are thermally

stressed and SCTLD is just becoming active on the reef. Therefore, a cautious interpretation of

the results is advised again for regions or zones with high bleaching prevalence (when paling is

included in the analysis) and where SCTLD was highly active.

Table 2. Total number of sites within each subregion recorded with mild, moderate or severe

bleaching (BL) and paling (P) prevalence.

Mild 0-20%Moderate

21-50%

Severe

>50%

North Palm Beach 6 45 3 2 1

South Palm Beach 9 100 1 5 3

Deerfield 2 49 2

Broward-Miami 65 1262 33 25 7

Biscayne 15 784 7 7 1

Upper Keys 27 1476 11 16

Mid-Upper Keys Transition 10 552 4 5 1

Middle Keys 18 968 13 5

Lower Keys 54 4510 32 13 9

Marquesas 31 3666 4 27

Dry Tortugas National Park 48 4232 1 25 22

Grand Total 285 17644 111 130 44

Total

Sites

Total

Corals

# of Sites with BL & P Prevalence

Subregion

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Figure 2. Bleaching and paling prevalence of surveyed coral colonies by subregion-zone.

The prevalence of disease was pooled by sites (Table 3) and by zones (Figure 3) within each

subregion. Prevalence values were broken into three categories: low (0-5%), medium (6-10%),

and high (>10%). All disease prevalence values were calculated from diseases with tissue loss

and do not include Dark Spot Syndrome or Discoloration conditions. Across the 285 sites

surveyed in 2019, 13 sites were recorded with medium disease prevalence and seven sites with

high disease prevalence (Table 3). The Broward-Miami subregion had the highest number of

sites with medium and high disease prevalence. Pooled by subregion-zone, the Deerfield inshore

reef was the only subregion-zone to experience high (>10%) disease prevalence (Figure 3). Two

sites were surveyed in the Deerfield subregion with only one on the inshore reef. Sixteen corals

were recorded at the Deerfield inshore reef site, four of which were diseased. All four

observations of disease were identified as ‘Unknown’ and occurred on the species Solenastrea

bournoni. All other subregion-zones were recorded with low disease prevalence (<5%).

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Table 3. Total number of sites within each subregion recorded with low, medium or high

disease prevalence.

Low 0-5%Medium

6-10%High >10%

North Palm Beach 6 45 5 1

South Palm Beach 9 100 8 1

Deerfield 2 49 1 1

Broward-Miami 65 1262 57 5 3

Biscayne 15 784 15

Upper Keys 27 1476 25 2

Mid-Upper Keys Transition 10 552 9 1

Middle Keys 18 968 18

Lower Keys 54 4510 49 4 1

Marquesas 31 3666 31

Dry Tortugas National Park 48 4232 47 1

Grand Total 285 17644 265 13 7

SubregionTotal

Sites

Total

Corals

# of Sites with Disease Prevalence

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Figure 3. Disease prevalence of surveyed coral colonies by subregion-zone. A larger scale inset

map of the Deerfield subregion was added to exemplify the high (>10%) prevalence of disease in

that subregion.

Across all sites surveyed in 2019, a total of 82 corals were recorded with SCTLD within the belt

transects. Seventy-three of those corals were in the Lower Keys subregion with 18 occurrences

on Siderastrea siderea, 12 on M. cavernosa, 10 on C. natans, 10 on O. faveolata, and five on P.

strigosa. All other species recorded with SCTLD in the Lower Keys had less than five

occurrences. Due to the high density of corals in the Lower Keys, however, disease prevalence

values were low at both the site and zone level.

Roving Diver Survey Results

In 2018, the DRM program implemented a Roving Diver Survey (RDS) to be completed if divers

had bottom time after completing two belt transects at a site. The purpose of the RDS was to

determine the presence of SCTLD on a scale greater than the 20m2 area surveyed in the belt

transects at each site. Due to the wide range of symptoms exhibited by corals with SCTLD,

surveyors were not asked to distinguish between the different types of diseases during the RDS.

Instead, surveyors tallied corals with any type of disease that resulted in active tissue loss and

corals that appeared healthy. The RDS data was used to identify the leading edge of SCTLD as it

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progressed westward, where corals with SCTLD lesions were most frequent (i.e. the location of

the “epidemic zone”) and how persistent SCTLD was in the “endemic zone” or regions in which

outbreak levels of SCTLD had concluded.

Across the Florida Reef Tract, 263 RDS were conducted during the 2019 season with a total of

8,550 corals tallied. Across all RDS surveys, a total of 783 corals were observed with active

tissue loss from disease, with 680 of those corals observed in the Lower Keys subregion (Table

4). Among the seven coral species targeted during the surveys, C. natans had the highest

occurrence of disease resulting in tissue loss. In the Lower Keys subregion alone, 316 diseased

C. natans colonies were tallied. The Broward-Miami subregion had a total of 44 diseased

colonies tallied, with over half recorded in the nearshore reef zones (inshore and inner reef;

Table 4). Thirty-two of the 44 diseased colonies recorded in the Broward-Miami subregion were

M. cavernosa.

Prevalence values of diseased corals tallied during the RDS were calculated for each site and

then categorized into low (0-5%), medium (6-10%), and high (>10%; Figure 4). High disease

prevalence was recorded at RDS sites within the Deerfield, Broward-Miami, Biscayne, Upper

Keys, Middle Keys, and Lower Keys subregions. The greatest number of sites with high disease

prevalence calculated from the RDS was in the Lower Keys. No diseased corals were recorded

during the RDS in South Palm Beach, potentially due to the low density of target coral species in

that area. All other subregions were recorded with less than 20 total diseased colonies tallied

during the RDS (Table 4). Without a standardized survey area or survey time for the RDS,

prevalence values should be interpreted with caution. Results from the RDS can vary based on

survey time, visibility, current, and diver-bias in survey pattern.

Table 4. Total number of colonies tallied during RDS and total percent diseased colonies of

the target species. Total coral tallies are pooled across subregions and subregion-zones.

Subregions

Healt

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Dis

ease

d

Healt

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Dis

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Healt

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Dis

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d

Healt

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Dis

ease

d

Healt

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Dis

ease

d

Healt

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Dis

ease

d

Healt

hy

Dis

ease

d

North Palm Beach --

South Palm Beach 1 2 1 1 14 0%

Deerfield 1 10 3 2 4 35%

Broward-Miami 3 1 28 1 5 18 493 32 40 5 27 5 7%

Biscayne 2 4 2 60 1 58 2 7 2%

Upper Keys 8 47 40 1 7 83 1 100 6 16 3%

Mid-Upper Keys Transition 15 11 8 41 53 1 3 1%

Middle Keys 36 2 16 2 9 3 196 6 75 6 42 3 5%

Lower Keys 256 316 101 26 70 11 33 12 718 93 305 135 118 87 30%

Marquesas 170 2 98 1 34 150 1350 1 154 2 258 1 0%

Tortugas--Dry Tortugas NP 326 2 69 67 1 168 1043 5 470 6 221 1%

Grand Total 817 323 376 30 237 13 380 12 4008 142 1257 167 692 96 9%

Roving Diver Survey Total Coral Tallies

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Figure 4. Disease prevalence at sites where RDS were completed. Roving Diver Surveys were

limited to seven target coral species (C. natans, D. stokesii, D. labyrinthiformis, M. meandrites,

M. cavernosa, O. faveolata, and P. strigosa).

SUMMARY

Overall, the results indicate that 2019 was a mild bleaching year when prevalence values were

combined for all subregion-zones (Figure 1). When corals recorded with paling are included,

bleaching values were moderate (21-50%) in over half of the subregion-zones surveyed (Figure

2). Severe paling was observed on the outer reef of South Palm Beach when pooled across the

four sites surveyed. However, none of these sites had more than five total corals. All pale

colonies recorded on the South Palm Beach outer reef were either Stephanocoenia intersepta or

S. siderea. When compared to last year, bleaching prevalence was slightly lower in 2019 than in

2018; however, when the values are inclusive of paling, 2019 bleaching prevalence values are

very similar to those in 2018 (Table 5).

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Table 5. Number of subregion-zones recorded with mild, moderate, or severe bleaching

prevalence, and combined bleaching and paling prevalence, for each DRM summer survey event.

*2017 does not include data from the IRMA rapid response effort.

Overall disease prevalence (calculated from the belt transects) was low in 2019, except at the

Deerfield inshore reef (Figure 3), where ‘Unknown’ coral disease (i.e., a disease not positively

identifiable as SCTLD or another disease) affected four S. bournoni colonies. S. bournoni is

known to be affected by SCTLD and is considered an intermediately susceptible species by the

Florida Keys National Marine Sanctuary. In intermediately susceptible species lesions can

develop several months to years after the highly susceptible species perish

(https://floridakeys.noaa.gov/coral-disease/).

From the belt transect results, SCTLD was recorded within four of the 11 subregions surveyed in

2019 (Broward-Miami, Upper Keys, Middle Keys, and Lower Keys). Almost 90% of those

corals were recorded in the Lower Keys subregion with the majority comprised of S. siderea, M.

cavernosa, C. natans, and O. faveolata (Figure 5). Of those species, C. natans is considered

highly susceptible to SCTLD, while the others are considered intermediately susceptible. Overall

prevalence values of SCTLD, when pooled by subregion-zone, was less than 3% in every

subregion-zone. When analyzed by site, one site on the Lower Keys forereef was recorded with

high SCTLD prevalence (11%) and one site on the Broward-Miami inner reef was recorded with

medium SCTLD prevalence (6%). All other sites surveyed in 2019 had less than 5% SCTLD

prevalence along the belt transects.

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Figure 5. Images of coral disease in the Lower Keys subregion. Top left: C. natans; top right: M.

cavernosa (photo credit: Lonny Anderson, NOAA); bottom left: O. faveolata; bottom right: S.

siderea (photo credit: Cory Walters, MOTE Marine Lab).

Although the overall prevalence of diseased corals was low in the Lower Keys (likely due to a

higher density of corals in that subregion, many of which do not contract SCTLD), the region

had the highest number of diseased corals recorded along the belt transects, totaling 104 colonies

(Table 3). The RDS supported this finding in the Lower Keys, where 31 of 54 sites surveyed

were recorded with high (>10%) disease prevalence and two sites with medium (6-10%) disease

prevalence (Figure 4).

The purpose of the RDS was to expand the survey area at a site beyond the 20m2 surveyed in the

belt transects, to better assess the presence of SCTLD. The larger survey area aided in

documenting the presence of tissue loss lesions on rare coral species affected by SCTLD. In

addition, depending upon the coral community composition at the site the prevalence of SCTLD

can be low during both the early onset of the disease or in later stages in the endemic zone if

SCTLD has already killed the highly susceptible species. The RDS provided a technique that

could be used to identify the arrival of SCTLD at a site and aid in tracking its western

advancement along the FRT. As stated above, RDS prevalence values should be interpreted with

caution since they were not standardized for survey area and time.

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At the conclusion of the 2019 DRM season on October 29th, the results indicated that the leading

edge of SCTLD was advancing towards the Marquesas subregion. Five sites within the Lower

Keys subregion that are west of Key West were recorded with SCTLD. This put SCTLD at the

eastern most boundary of the Marquesas subregion during the month of October, when surveys

were completed.

For more information about FRRP and its DRM effort see the website

http://ocean.floridamarine.org/FRRP/. For more information about the Summer 2019 DRM

results contact Jennifer Stein at Jennifer.Stein@MyFWC.com or at (305) 676-3252.